To electrically connect to a circuit board, large-scale electronic components are commonly mounted in a socket soldered to the circuit board instead of being directly soldered to the circuit board. The socket has multiple contacts on a first surface of a housing which contact contact pads arranged on a bottom surface of the electronic component. Multiple solder balls corresponding to the contacts are disposed on a second surface of the housing.
A liquid crystal polymer (LCP) resin is often used for the socket housing. The LCP resin, however, has a coefficient of thermal expansion different from that of the circuit board. In modern applications, a large-scale CPU may have as many as three thousand contact pads two-dimensionally arranged with a pitch of 1 mm on the bottom surface. If the housing of the socket for such a large-scale electronic component is made of the LCP resin, the difference in coefficient of thermal expansion between the LCP resin and the circuit board may cause a soldering portion to crack or may cause the socket to warp when the socket returns to ordinary temperature after being soldered to the circuit board.
Accordingly, using the same material as the circuit board for the housing of the socket is contemplated for avoid warping for large-scale electronic components. In the housing of the socket, through-holes having inner wall surfaces plated with a conductive material are formed in order to electrically connect top and bottom surfaces of the housing. The passageways are circular holes. The contacts of the socket, however, are stamped or otherwise formed from a metal sheet.
Japanese Patent No. JP-H10-162909A discloses a connector having a housing and contacts press-fitted in the housing. Each connector has a solder ball attached to the lower end. In JP-H10-162909A, however, a gap is present between a press-fit portion of the contact and a press-fit hole of the housing. For this reason, solder from the solder ball melted when the socket is soldered to the circuit board may flow up through the gap, causing insufficient soldering to the circuit board.